I. Technical Field
The present invention relates to a near-field optical head, and a near-field optical head device, a near-field optical information device and a near-field optical information system provided with the same, and relates to a device capable of recording or reproducing information at a higher density in or from a medium.
II. Description of the Related Art
In the field of optical information recording, notice has been taken of optical recording using a near field light. The prior art described in Japanese Patent Laid-Open Publication No. 2004-151046 presents a method for making a higher-density record with a near field light. FIGS. 13 to 15 show the configuration and main part of a near-field optical head device according to the prior art.
In FIGS. 13 and 14, a near-field optical probe slider 702 facing a disk 701 as a recording medium is provided with beam-condensing elements integrated therein and receives a parallel beam from an optical head 703. A carriage actuator 704 moves the optical head 703 in radial directions of the disk 701. A beam emitted from a semiconductor laser 708 as a light source passes through a collimating lens 709 and a beam-shaping prism 710 to become a circular parallel beam in the optical head 703 and is incident upon the near-field optical probe slider 702 through a beam splitter 712 and a mirror 714. The near-field optical probe slider 702 is subjected to an adjustment of the position thereof in the tracking directions by a piezo-electric element 711 and pressed onto the disk 701 by the force of a suspension 705 attached thereto.
FIG. 15 is a schematic side view of the near-field optical probe slider 702 provided with a scattering body 21 facing a disk 27 as a recording medium and a substrate 24 supporting this. The scattering body 21 and the substrate 24 are arranged on the near-field optical probe slider 702 in such a way that the distance between the scattering body 21 and the disk 27 is kept below tens nanometers. Light radiated from a light source 19 is incident upon the scattering body 21 through a collimating lens 18 and a beam-condensing element 17 to thereby generate intense near field light at the part of the scattering body 21 proximate to the disk 27. If the disk 27 is provided with a phase-change material, the near field light generated from the scattering body 21 changes the crystal phase into an amorphous phase to thereby form a record mark.
On the other hand, the reproduction is conducted, as shown in FIGS. 13 and 14, by detecting a variation in the intensity of light returning from the disk 701, more specifically, because the percentage of the near field light scattered by the disk 701 varies according to the presence of the record mark, by detecting a variation in the intensity of the scattered light. In practice, the light (signal light) from the disk 701 is split from the incident light by the beam splitter 712 and detected by a detector 717 after passing through a condensing lens 715. In the prior art, the polarization direction of the signal light from the disk 701 differs from the polarization direction of the incident light, thereby improving the contrast by setting the polarization direction of a polarizer 716 on the optical path perpendicular to the incident-light polarization direction.
However, in the near-field optical head device according to the prior art, the near-field optical probe slider 702 provided with the scattering body 21 generating a near field and the optical head 703 provided with a light source exist individually, thereby hindering miniaturizing the near-field optical head.
Specifically, in order to keep the distance between the scattering body 21 and the disk 27 shorter than several tens nanometers, the near-field optical probe slider 702 needs to be smaller and to be provided only with the scattering body 21 and the substrate 24 thereon, thereby meaning that the near-field optical probe slider 702 and the optical head 703 have to be separately formed by an individual member. Besides, in order to send a beam emitted from the semiconductor laser 708 as a light source to irradiate the whole main surface of the scattering body 21 parallel to the disk 701, the emitted beam from the semiconductor laser 708 needs to be incident from behind the scattering body 21, thereby requiring many optical devices such as the collimating lens 709, the beam-shaping prism 710, the beam splitter 712 and the mirror 714. This makes the optical head 703 and the whole near-field optical head larger.